Sugars, such as sucrose, fructose and glucose, are utilized to provide a pleasant taste to beverages, foods, pharmaceuticals, and oral hygienic/cosmetic products. Sucrose, in particular, imparts a taste preferred by consumers. Although sucrose provides superior sweetness characteristics, it is caloric. Non-caloric or lower caloric sweeteners have been introduced to satisfy consumer demand, and there is desire for these types of sweeteners that have favorable taste characteristics.
Stevia is a genus of about 240 species of herbs and shrubs in the sunflower family (Asteraceae), native to subtropical and tropical regions from western North America to South America. The species Stevia rebaudiana, commonly known as sweetleaf, sweet leaf, sugarleaf, or simply stevia, is widely grown for its sweet leaves. Stevia-based sweeteners may be obtained by extracting one or more sweet compounds from the leaves. Many of these compounds are steviol glycosides, which are glycosides of steviol, a diterpene compound. These diterpene glycosides are about 150 to 450 times sweeter than sugar.
Examples of steviol glycosides are described in WO 2013/096420 (see, e.g., listing in FIG. 1); and in Ohta et. al., “Characterization of Novel Steviol Glycosides from Leaves of Stevia rebaudiana Morita,” J. Appl. Glycosi., 57, 199-209 (2010) (See, e.g., Table 4 at p. 204). Structurally, the diterpene glycosides are characterized by a single base, steviol, and differ by the presence of carbohydrate residues at positions C13 and C19, as presented in FIGS. 2a-2k. See also PCT Patent Publication WO 20013/096420.
Typically, on a dry weight basis, the four major steviol glycosides found in the leaves of Stevia are dulcoside A (0.3%), rebaudioside C (0.6-1.0%), rebaudioside A (3.8%) and stevioside (9.1%). Other glycosides identified in Stevia extract include one or more of rebaudioside B, D, E, F, G, H, I, J, K, L, M, N, O, steviolbioside and rubusoside.
While the major steviol glycoside Reb A is commonly used as sweetener in beverage applications it has off-taste issues. More recently, there has been focus on certain minor steviol glycosides which have better taste properties. For example, rebaudioside M has higher sweetness intensity and is more potent than other steviol glycosides (e.g., see Prakash, I., et al. (2013) Nat. Prod. Commun., 8: 1523-1526, and WO 2013/096420). Rebaudioside D tastes about 200-220 times sweeter than sucrose and in a sensory evaluation it had a slow onset of sweetness and was very clean (e.g., see Prakash, I., et al. (2012) Int. J. Mol. Sci., 13:15126-15136).
Some minor rebaudiosides can be challenging to use because they have less than desirable water solubility properties. For example, it has been reported that Reb D is difficult to use in food products because of its low solubility in water at room temperature. For instance, Reb D needs to be heated to near boiling water temperature for 2 hours in order to achieve complete dissolution at 0.8% concentration. At most only 300 to 450 ppm can be solubilized in water at 23° C. (e.g., see US 2013/0251881). As another example, rebaudioside M obtained from Stevia rebaudiana has poor aqueous solubility and dissolution qualities in beverage formulations (e.g., see US 2014/0171519).
Certain methods to improve rebaudioside solubility are less than desirable because they are labor intensive, requiring high processing temperatures and the use excipient compounds. For example, see WO 2013148177.